QRZ Forums. I have been given a half built linear without a schematic which has bases for 4 x b tubes.
Can anyone point me in the direction of a schematic for such a 4 x please? This is just an experimental excercise. I know it would only produce - watts but that's immaterial as I have already a home-built 2 x linear should I need big boots. Thanks for reading.
G4FUTDec 27, I could draw one given an hour or so, but short of that: Four Bs should produce at least W output power, and the design wouldn't be much different from using two of them, except the plate impedance is lower so the output tank circuit would need small modification.Seeing someone elses doppelganger in a dream
I'd think on lower frequencies like 80m if you have a bandswitched pi-net, it would still work with four tubes. On a higher frequency like 10m, possibly not.
Did you try using the four tubes? I haven't tried putting 4 into the tube sockets as yet, but will of course and see what happens. As I said, this is just an experiemntal excercise. I noticed that the original builder hadn't placed any parasitic supressers SP?
Anyway, I look forward to hours of fun messing about with this. G4FUTDec 28, OK latest is that after spending a few hours this morning, I've brought the spare two sockets into the circuit, all connected up. But first I'll need to sort out the relay and then test the rig using only two tubes first.
Nice job, it looks really good. AF6LJDec 28, The photo shows very nice workmanship. I might be missing it, but I don't see any coils in there that look like they'd have enough inductance for 80 meters, and maybe not even for 40 meters. Are all the parts there? When you switch to 40m or 80m, is there an obvious inductor switched into the pi-network? Also, that 5-section RF choke "looks" like it's for something that's very low-powered.
Can't see it that well but it appears to be wound of very fine wire that may not handle mA that would be drawn by four s.
Looks can be deceiving, but what kind of wire gauge is that choke wound from?Back to Dr. If you have any questions or comments, you can send E-Mail to Dr. Greg Latta at glatta frostburg. Plate and 10m Tank Coil Construction Details. Interior Photos of the Finished Amplifier. Amplifier Schematic Diagrams and Circuit Descriptions. The signal from the input jack travels via RG coaxial cable through relay K1 to the input link L1which consists of three turns of insulated hookup wire on coil L2.
L2 is tuned to resonance by the grid tuning capacitor C1. The transformer action of L1 and L2 steps up the voltage, matching the low impedance of the driving transmitter to the high impedance input of the tube. If extra driving power is available, as is the case with the 6CL6 transmitterthe grid tuning control is used as a drive level control, and is tuned off resonance to reduce the drive to an acceptable level.
Grid bias is fed into the bottom of L2 and travels through L2 and the 15 ohm resistor to the grid of the tube. The 15 ohm resistor helps to load the grid and provide additional stability.
Since capacitor C1 carries the negative grid bias, C1 must be insulated from ground and an insulated coupling must be used on its shaft. Plate Feed Circuit: In an RF amplifier it is necessary to supply DC plate voltage to the tube about volts in this case and at the same time extract the amplified RF that appears at the plate of the tube.
At the same time, the uuf plate coupling capacitor at the top in the schematic permits the RF on the plate to flow though to the output tank circuit while blocking the plate voltage.
The 0. The ohm resistor and small coil RFC2 in series with the plate lead form a parasitic suppressor, which helps prevent unwanted oscillations.Shiny widget checkbox
Neutralization Circuit and Procedure: Though screen grid tubes are inherently more stable than triodes and may in some cases be used without neutralization, good amplifier design demands that they be neutralized, especially in a multiband amplifier.
The neutralization is accomplished by intentionally feeding some of the output signal back to the input out of phase. This cancels the positive feedback that occurs between the plate and control grid of the tube. Capacitive feedback is used, since the amount of feedback will then be independent of frequency.Pi-in 5W, P o -out W.
Being a passive-grid amplifier, most of the input power is dissipated in a non-inductive carbon resistor applied to the control-grid of the valve. This type of linear has many desirable features, including low cost, low component count, stability due to the swamping effect of the passive grid input load and simplicity of the construction. Because the control grid is loaded with a resistor, the amplifier is in principle stable. With 10 W input the output is about - W.
Full size. Later in this article is a simpler design. The transceiver is loaded correctly without variable input tuning. After band changing, only two capacitors need to be tuned. In this circuit sweep-valves are being used. Hams not having much experience with valves may learn much from this project. One day they may want to build a high-powered amplifier with a "real" transmitting valve.
I leave it to the pro's to argue about which specific valves should be used in this project; when properly adjusted, every amplifier will behave linearly.Hyundai 4g63 valve cover
When cooled sufficiently, these sweep-valves are nearly impossible to destroy. They especially can withstand high voltages and peak currents. In contrast with American sweep tubes they will even function well with anode voltages far in excess of Volts, even with V the valve survived many experiments.
In order to protect you from extra problems, I am advising you to apply only with — Volts.
The valves may be mounted vertically or horizontally, the choice giving more freedom of layout. EL and EL, which are used much in 27 MHz linear amplifiers, only differs in filament voltage: 6.
One should reckon with valve diameters differing with different makes: e. The valve seems to be virtually indestructible with its performance limited only by envelope temperature. After ten years or more television service, cathode emission remains near perfect and the PL is capable of sustaining over 1.
The anode is in fact about the same size as that of the old and A power valves. Although, in the case of the PL, closer to its glass envelope. This is why forced air-cooling is needed to get maximum power from this valve.The transmitter had an output of 1. A homebrew amplifier with watts of output would make a big improvement on the air, and seemed like the ideal follow up project. I had to do a lot of research to find a design for the amplifier. This was ideal for my purposes, and it looked like I could scrounge up all of the necessary parts, except for the grid input circuit, which was a commercially available in sub-assembly.
Though easy enough to buy inthe chances of finding such a unit several decades years later were about zero. I would have to design my own input circuit or borrow one from another design. After doing some more research, I found a design for a watt amplifier in the ARRL handbook that used a pair of tubes. Though the input impedance for a single would be twice that of a pair, I figured that the input circuit would still work, especially since I would have a lot of extra drive available from the 6CL6 transmitter.
The resulting design is thus the handbook design with the input circuit from the design. For the power supply I used the same design as the amplifier, but with solid state, rather than tube, rectifiers. In these pages, which will be in a constant state of improvement, are pictures of the amplifier and its various parts.Powershell get day of week
Eventually, circuit diagrams, circuit explanations, and the history and details of the design and construction will be included. Please check back from time to time.
Back to Dr. If you have any questions or comments, you can send E-Mail to Dr. Greg Latta at glatta frostburg. Plate and 10m Tank Coil Construction Details. Interior Photos of the Finished Amplifier. Amplifier Schematic Diagrams and Circuit Descriptions. The same chassis construction used on the transmitter was also used on the amplifier.
Matching knobs were purchased from Radio Shack. The gold cage on the transmitter was made from decorative sheeting left over from a kitchen remodeling project. The cage protects the operator from high voltage and also keeps RF inside the transmitter. Click on the image for a larger view. Click here for a super detailed view.
HF Tube Amplifiers
Front View: In this view of the amplifier the knob at the top of the upper panel is the bandswitch for the plate tank circuit and the left knob on the bottom panel is the band switch for the grid circuit. Changing bands requires that both switches to be set to the same band. Using separate band switches makes band changes a little more awkward, but it simplifies construction and provides much better isolation between the input and output circuits, yielding an amplifier that is more stable.
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All bands easy HF linear using tubes. Moreover the anode voltage is kept low v in comparison to other circuits I have seen.
The author tends to use components that are not very hard to find even these days. It seems to me easier and possibly cheaper to build such a tube amplifier rather than a transistorized one at these power levels ironic! A single stage that can provide so much gain with a moderately low anode voltage, seems attractive.
Can you please comment on this circuit? I am sure there are other circuits out there, can you please notify me of some of these, based on my comments above ease of construction, low anode voltage, high gain etc.
Last edited: Sep 29, For the watt level I would go with a solid state amplifier and switching power supply. The advantage is lighter weight, smaller foot print and cooler operation and should be better from lower heat inside the cabinet, for custom building and no tuning band to band. I just recently built up a single band station that uses a solid state amplifier and a switching supply that runs 28 volts.
I did not build the pieces but put together what I could find for that band. The results are outstanding for performance and reliability so far. The amp is driven with a Transverter and from an outside radio off the 10 meter band for conversion up and down. The amp has 1 bi polar UHF transistor input stage and 2 FET stages to attain this kind if gain on 28 volts from a fully shielded switching supply.
I decided not to make any changes to the amplifier as built but use 40 db of adjustable attenuation at the input to control power over a wide range. That way the TV could be used at it's output level without any changes by bypassing the amplifier. I know this is not an all band project but some of the thoughts may be helpful in your final project decisions. My total physical size is not small by any measure because I did not build to that end but assemble the units as they were built, onto a frame.
My equipment looks like a vertical computer of older vintage to keep from taking up so much space. The stability of stations I hear during contests is terrible. This project has 3 contests beside regular use already with no faults showing up.
All three units are fan cooled as is the driver radio a Kenwood TS The antenna for this band are stacked beams. The gain and directivity are very good for small 9 elements each, array vertically spaced at 7 feet apart with harnesses custom built to match the beams to a common 50 ohm feed point between them. I'm sure your building for the pleasure of accomplishment as I did for the band of which there is not a great deal of equipment to select from to get all mode operation.
Good luck. KM3FOct 1, WA7PRC and deleted member like this.I am using TC without modification getting watts ssb rf power out on 14mhz.
KL703 25-30MHz 500W Linear Amplifier (New)
Dear Shiva, Thanks for your msg. TC is basically class C amplifier. During it's operation in ssb, the audio will not be as smooth as class AB amp. Every half cycle ,there may be a slight distorsion noticed.
Metering of a Grounded Grid Amplifier
In the case of class AB amp biased like all commercial TX, bias current to 25o mAthe audio will be smooth. Please provide this details. Specially designed for CB Radios. Madhu Mohan is my tech consultant for this project. Anil George. Dear Anil, Thanks for your msg. In ssb operation both will have similar problem in audio quality with adopted class c type. In this no pre amp inclued as in KL At the outset I commend you this nice project.
The prototype version looks very professional. Amateurs who operate portable will find this exciting especially since the current drawn at 25W RF out is around 4 Amps Will appreciate knowing on what bands these tests in the test report were carried out.
Did you notice that the performance was similar across the spectrum?Sound masking
Are you planning to incorporate any BPF's or filtering in the final version? Looks great! What about SWR protection? Is it not a must? I really appreciate the effort.Skipper by Palomar 4 tube 6146w linear amplifier
The set-up and circuit diagram look quite inviting. In future, I would like to own one.
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